I didn't play much on the Wii, so many of these are "games I like that happen to be on the Wii":

House of the Dead: OverkillDisaster: Day of CrisisSuper Smash Bros BrawlDJ Hero 2OkamiSin and Punishment: Successor of the SkiesNo More HeroesLego Indiana JonesLego Harry Potter Years 1-4Lego Star Wars: The Original Trilogy

As far as level design goes Galaxy 2 is just Galaxy but taken further. The only reason to prefer the original is if you thought the story aspects were better...and to be honest they were, but its not what I play Mario for.